The present invention relates to a method to prevent explosions in closed tanks which hold flammable liquids and flammable vapors and air above these liquid fuels. More particularly, the invention is directed to the prevention of explosions in aircraft fuel tanks.
Because of recent unexplained aircraft explosions, there has been a renewed interest in controlling fires aboard aircraft. One particular possible source of aircraft fires, and particularly explosions, is the fuel tanks on the airplane. Under normal operating conditions there exists an explosive mixture of vaporized fuel or fuel components and air in the space above the liquid fuel, referred to as the ullage. If this mixture is exposed to a flame source, such as a spark, the vapors can ignite in an explosive manner, causing a rupture of the tank, rapid expansion, vaporization and ignition of the liquid fuel and a destruction of the aircraft. Current aircraft fire prevention techniques consists primarily of the release of flame retardants such as halogenated hydrocarbons, including CCl.sub.4, CF.sub.4, FREONS, or HALONS (broadly referred to as chloro-fluorohydrocarbons), following flame ignition. In most cases, particularly in the case of a fuel tank ignition, this response is too late as the ignition rapidly evolves into an explosion.
Thus there is a need to prevent ignition of the fuel vapors rather than extinguishing them after they are ignited.